When you deploy Scrapyard Crawler, remove up to 3 cards in your opponent's scrapyard from the game.Scrapyard Crawler gets +1 firepower and +1 hull for each crew card removed this way.
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Explained
When you deploy Scrapyard Crawler, remove up to 3 cards in your opponent's scrapyard from the game.301.8, 403.4
It happens as soon as it is deployed, while it waits in the crossfire, and at once: no one can react to it. Put on board without being deployed, as by Resurface, it doesn't happen (301.8). You choose which when it happens: any cards, from none to 3. They are out of the game for good (403.4).
Scrapyard Crawler gets +1 firepower and +1 hull for each crew card removed this way.301.9
It keeps the bonus as long as it stays on board and loses it when it leaves (301.9). The extra hull counts for the Ironclad engine: with 3 crew removed it has 4 hull (603.8a).